abruptly vs on the spur of the moment

abruptly and on the spur of the moment both are adverbs.

Word	Noun	Adjective	Verb	Adverb
abruptly	No	No	No	Yes
on the spur of the moment	No	No	No	Yes

As adverbs, abruptly and on the spur of the moment are synonyms defined as:

abruptly and on the spur of the moment: quickly and without warning
abruptly and on the spur of the moment: happening unexpectedly
abruptly and on the spur of the moment: on impulse; without premeditation

Other synonyms of abruptly include all of a sudden, dead, of a sudden, short, suddenly.

abruptly (adverb)	on the spur of the moment (adverb)
quickly and without warning; happening unexpectedly; on impulse; without premeditation	quickly and without warning; happening unexpectedly; on impulse; without premeditation